In recent years, the semiconductor device has been made to exhibit a higher function and have a more highly integrated structure, and has been mounted on a variety of electronic equipment. Additionally, the semiconductor device has brought greater facility to the life in society and become necessary and essential for the life in society. Thus, a fault of the semiconductor device might have a higher possibility to cause a serious damage to the life in society. Therefore, the reliability is a quite essential factor for the semiconductor device.
The semiconductor device has been loaded on a variety of electronic equipment. Accordingly, the environment in which the semiconductor device is used has also changed variously. Furthermore, the outer dimension of the semiconductor device varies depending on the electronic equipment on which the semiconductor device is loaded. In particular, in recent years, a package of the semiconductor device has been gradually miniaturized and formed into a thinner type.
As an example of such a package for the semiconductor device, an SOJ (Small Outline J-Leaded Package), QFP (Quad Flat Package) or SOP (Small Outline Package) type is known, in which external lead wires extend from each side of the semiconductor device. Otherwise, a QFN (Quad Flat Non-leaded Package) or SON (Small Outline Non-leaded Package) type, in which external lead wires extend from a bottom portion of the semiconductor device, is also known.
In either of such packages for the semiconductor device, the semiconductor chip is loaded on a top surface of a die pad of a lead frame. In this case, a lead part of the lead frame is electrically connected with the semiconductor chip via bonding wires. In addition, the lead frame, semiconductor device and bonding wires are sealed together by an electrically insulating resin such that a part of the lead part of the lead frame can be exposed outside. The semiconductor device including such a package is commonly referred to as a resin-sealed (type) semiconductor device.
In such a semiconductor device including the resin-sealed semiconductor package, there should be an interface, at which the die pad and the lead part, both formed from a metal as parts of the lead frame, are in contact with the sealing resin. In this case, there is a problem of adhesion strength (or joining strength) between the metal and the resin in such an interface region.
If the adhesion strength between the die pad and lead part of the lead frame and the sealing resin is substantially low, peeling between the die pad and lead part of the lead frame and the sealing resin may tend to occur, thus causing a crack in the sealing resin due to such peeling, and even bringing the semiconductor device into a fault, during a manufacturing process of the semiconductor device, during a process of assembling the semiconductor device onto an implementing substrate (or printed circuit board) that will be further mounted onto the electric equipment, and/or during use of such electronic equipment. That is to say, due to lack or insufficiency of the adhesion strength between the die pad and lead part of the lead frame relative to the sealing resin, the reliability of the semiconductor device will be deteriorated.
Research and development for addressing or solving such problems have been reported in, for example, the Japanese Patent Laid-Open Publication No. 2000-269401 (see, for example, claim 1) and the Japanese Patent Laid-Open Publication No. 11-40720 (see, for example, claim 1 and paragraph [0008]).
The Japanese Laid-Open Patent Publication No. 2000-269401 A1 discloses a plurality of semi-spherical dimples formed on both a top surface and a bottom surface of the die pad of the lead frame. With such a lead frame, a joining area between the lead frame and the sealing resin can be substantially increased. As a result, positive improvement of the adhesion strength between the lead frame and the sealing resin can be expected. In this case, however, no measure is taken for the lead part of the lead frame. Accordingly, the adhesion strength at the interface between the lead part and the sealing resin cannot be enhanced. In particular, the interface between the lead part and the sealing resin is exposed to the outside air. That is to say, the adhesion strength, at such an interface through which moisture or the like may first penetrate, is left unimproved in such a level that has been conventionally seen. Therefore, the reliability of the semiconductor device cannot be sufficiently improved.
The Japanese Laid-Open Patent Publication No. 11-040720 A1 discloses roughening of a surface of a resin sealing region of a lead frame material as well as application of Ni plating and Pd plating, in this order, to the roughened surface. In this case, in a face roughening process of a copper-alloy material, an organic-acid type etching liquid (e.g., in one embodiment, a micro-etching liquid CZ8100 produced by MEC Co., Ltd.) is used. In fact, the organic-acid type etching liquid is effective in the ease of roughening a copper surface formed by plating. Furthermore, the organic-acid type etching liquid can also enhance a degree of roughening the surface of a rolled copper plate or rolled copper-alloy plate, such as the lead frame material. However, in the case of using the organic-acid type etching liquid for the rolled copper plate or rolled copper-alloy plate, such as the lead frame material, it will be impossible or quite difficult to form a surface profile including finely pointed needle-like projections. Accordingly, it will also be impossible to sufficiently enhance the adhesion strength between the lead frame formed from the rolled copper plate or rolled copper-alloy plate and the sealing resin.
In order to secure enough the reliability of the semiconductor device, it is important not only to enhance the adhesion strength between the circuit member and the sealing resin but also to enhance adhesiveness between the lead part (or internal leads) and the bonding wires for electrically connecting the lead part of the circuit member to the semiconductor chip. Besides, it is also important to enhance the adhesiveness between the lead part (or external leads) and soldering portions for electrically connecting the lead part of the circuit member to the implementing substrate (or printed circuit board). Furthermore, it is also important to enhance sealing ability of the sealing resin to the circuit member. In addition, improvement of other properties of the circuit member may also enhance the reliability of the semiconductor device including the circuit member.